Reducing Pesticide Use in Honey Bee Colonies through Sound Sampling and Treatment Procedures

Annual Reports

Commodities

Animals: bees

Practices

Animal Production: parasite control

Crop Production: application rate management

Pest Management: economic threshold, prevention

Abstract:

We developed a sampling plan to help beekeepers monitor Varroa destructor mite infestations in honey bee colonies. From a sample of 280 adult bees, collected using our novel sampling device, beekeepers can estimate the total mite density in a colony (mites on adults and those reproducing on pupae). Standard sampling will help beekeepers make educated treatment decisions. Field trials of bees bred for both Hygienic Behavior and Varroa Sensitive Hygiene had significantly lower mite levels compared to an unselected line of bees demonstrating that the hygienic trait can reduce mite loads and thus the frequency of pesticide application.

Introduction:

The North Central region of the US, particularly MN, ND and SD are the top honey producing states based on yield per colony, together producing over 30% of the total honey production for the nation. The majority of the commercial beekeepers in the Upper Midwest are “migratory,” meaning that they transport their colonies every winter either to southern states where they produce bulk bees and queens for sale, or to CA and other states where the bees pollinate almond orchards and other fruit and vegetable crops. The beekeepers transport their colonies back to the Upper Midwest for the summer to produce large honey crops.

The honey bee, Apis mellifera, population has been declining since introduction of the parasitic mite Varroa destructor in 1987. Varroa is a devastating pest. The mites weaken individual honey bees, increasing the bee’s susceptibility to the effects of disease and poor nutrition. Infected colonies die in 1-2 years. To prevent potentially large colony losses, many beekeepers have resorted to using pesticides (organophosphates and pyrethroids) within their colonies. Many treat all their colonies with pesticides once or twice a year, irrespective of mite level. The treatments add a great operating expense for the beekeepers, increase the risk of contamination of hive-products (Frazier et al., 2008), pose health risks to bees (Currie, 1999; Rinderer et al, 1999; Haarman et al., 2002; Collins et al., 2004), and the mites have developed resistance to the synthetic pesticides. To minimize these negative effects, beekeepers have expressed their desire to decrease the number of treatments. Many beekeepers have heard of the integrated pest management practice of treating only when economically necessary, but this requires sampling to determine the current mite levels and having a treatment threshold. Prior to this research, beekeepers lacked a standard, accurate and efficient way to sample mites in a honey bee colony. Our goal is to encourage beekeepers to sample their bee colonies for mite pest populations in a standardized way to help them make wise treatment decisions and reduce pesticide use. Such a sampling plan for a mite pest in an insect colony has never been attempted before.

Once a beekeeper samples to find the mite infestation, that beekeeper will need to make a treatment decision. Treatment thresholds of 10-12% colony mite infestation have been developed (Martin 1998, 1999; Delaplane and Hood, 1997, 1999). However, the thresholds were created based on mite levels in relatively small-scale beekeeping operations (hobby or side-line) in which the colonies are maintained in one location year round. Migratory beekeepers, those that move their colonies across the U.S. for honey production and to fulfill pollination contracts, would also benefit greatly from a treatment threshold. These commercial beekeepers will likely treat at a lower threshold because their livelihoods depend on it. Transporting bees en masse leads to increased horizontal transmission of diseases and pests, and nutritional stress, which may decrease the colonies tolerance for the mite. Bees with natural mite resistance due to hygienic behavior may have a different treatment threshold than susceptible colonies. There should be an absolute lowest threshold (e.g. 2-5%) where below that level no beekeeper should need to treat. Between the low threshold and the 10-12% threshold is a gray area where a beekeeper should make a decision based on the nature of their beekeeping operation, and their personal tolerance for colony loss. Monitoring mite loads is a first step in helping beekeepers understand their mite levels and dynamics. With this system and good record keeping, beekeepers can find the treatment level works best for them based on their own operation.

Project objectives:

The objective of this project was to encourage beekeepers to reduce the use of in-hive chemicals by monitoring mite populations through sampling, helping them to make informed treatment decisions, and demonstrating the benefits of keeping bees with natural resistance to the mite. The reduction of treatments will help beekeepers avoid unnecessary costs, pesticide residues, and help slow the evolution of resistance of the mites to chemicals; thereby fostering more sustainable beekeeping practices, increasing the profitability of beekeeping, improving environmental quality, and promoting pollinators.

Objective 1. Develop a simple and standardized sampling plan for commercial beekeepers to help them determine the economic treatment level for Varroa destructor mites.

Objective 2. Develop published guidelines for migratory beekeepers on making educated treatment decisions for the mite based on the sampling plan.

Objective 3. Compare mite levels between our line of bees bred for both Hygienic Behavior (HYG) and Suppression of Mite Reproduction (SMR) with an unselected, commercial line of bees, to demonstrate that the use of resistant bees can reduce mite loads and thus, the frequency of pesticide application.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.

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